Machines for forming coil springs from continuous wire are well known in the prior art. In the manufacture of mattresses and upholstered furniture that use arrays of coil springs, machines have been employed in the prior art that form a plurality of springs from a continuous length of wire. One such machine is disclosed in British Patent No. 937,644 to Willi Gerstorfer entitled "Improvements in or relating to Machines for the Manufacture of Compression Spring Strips from Wire, for example for Upholstery Inserts." The machine of the Gerstorfer patent is operative to manufacture from a continuous length of wire a plurality of interconnected compression springs comprising alternate left and right hand coil springs joined by an integral straight length of wire. The machine of the Gerstorfer patent employs a coil forming device having moveable linkages to shift the settings of the machine to coil the continuous wire. The Gerstorfer machine is particularly useful in forming from continuous wire a multiple coil spring having coils of alternating direction or hand. To form such springs, the Gerstorfer machine coils the wire alternately in first one direction and then the other, with each coiling direction being followed by the feeding of a length of straight wire, which forms an interconnecting head between adjacent coils.
As coil springs are manufactured from a continuous strand of wire, a continuous spring with interconnected coils is formed. As this continuous spring moves downstream from the coil forming device, it acquires a torsional build-up that increases as the formed wire spirals away from the coil forming device and moves toward a take-up reel. If the coiling of the formed spring is entirely or predominantly in one direction, accumulated torsion or a twisting is produced downstream of the coil forming device that must be relieved. To accommodate this potential accumulated torsional build-up the Gerstorfer machine oscillates the forming device over 180.degree. so that the imparted twist is in first one direction and then the other. As a result, the accumulated twist or torsion in the formed multiple coil spring is that of, at most, the number of turns of one coil. In the Gerstorfer machine, the formed spring also exits the forming device in one direction regardless of the direction of the formed coil.
Such oscillation of the forming devices has the disadvantage of limiting the speed at which the forming device can operate. It also produces an undesirable flipping of the formed spring from one side to the other at the exit of the forming device, which flipping produces a high centrifugal force on the spring that must be controlled. As a result, spring forming machines that employ the coiling devices and forming methods such as those of the Gerstorfer patent are insufficiently fast to supply an assembly apparatus. Typically, six to eight coil forming machines may be required to supply one assembly apparatus. Thus, the spring must be coiled and then later supplied to an assembling apparatus, and then loaded on the assembler in a time consuming process. Furthermore, defects in a spring may not be discovered until an entire defective reel is formed and later proves unusable when assembly is attempted.
By utilizing a Gerstorfer type coil forming machine in such a way as to eliminate the need to oscillate the forming device, it has been found that significant increases may be made in the speed at which the forming machine can operate. One such approach is, for example, disclosed in the commonly assigned Adams, et al. U.S. Pat. No. 4,112,726. The method and apparatus of the Adams et al. patent, produces, from a continuous coil spring, multiple coil spring assemblies by forming intermittent spring heads at intervals along a preformed continuous single coil spring, and then bending the coils to face first one direction and then the other. The springs so formed, however, are all of the same rotational direction or hand and, accordingly, must be linked by diagonally oriented heads. Such springs require very complex machinery to form and assemble the springs into assemblies.
Accordingly, there is a need in the spring manufacturing art to provide for the manufacture from continuous wire of spring assemblies, particularly those having coils of alternating hand or rotational direction which can be achieved rapidly, particularly without the need to oscillate the coil forming device.